com.google.gson.internal.ConstructorConstructor Maven / Gradle / Ivy
The newest version!
/*
* Copyright (C) 2011 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.gson.internal;
import com.google.gson.InstanceCreator;
import com.google.gson.JsonIOException;
import com.google.gson.ReflectionAccessFilter;
import com.google.gson.ReflectionAccessFilter.FilterResult;
import com.google.gson.internal.reflect.ReflectionHelper;
import com.google.gson.reflect.TypeToken;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;
import java.util.EnumMap;
import java.util.EnumSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Queue;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentNavigableMap;
import java.util.concurrent.ConcurrentSkipListMap;
/** Returns a function that can construct an instance of a requested type. */
public final class ConstructorConstructor {
private final Map> instanceCreators;
private final boolean useJdkUnsafe;
private final List reflectionFilters;
public ConstructorConstructor(
Map> instanceCreators,
boolean useJdkUnsafe,
List reflectionFilters) {
this.instanceCreators = instanceCreators;
this.useJdkUnsafe = useJdkUnsafe;
this.reflectionFilters = reflectionFilters;
}
/**
* Check if the class can be instantiated by Unsafe allocator. If the instance has interface or
* abstract modifiers return an exception message.
*
* @param c instance of the class to be checked
* @return if instantiable {@code null}, else a non-{@code null} exception message
*/
static String checkInstantiable(Class c) {
int modifiers = c.getModifiers();
if (Modifier.isInterface(modifiers)) {
return "Interfaces can't be instantiated! Register an InstanceCreator"
+ " or a TypeAdapter for this type. Interface name: "
+ c.getName();
}
if (Modifier.isAbstract(modifiers)) {
// R8 performs aggressive optimizations where it removes the default constructor of a class
// and makes the class `abstract`; check for that here explicitly
/*
* Note: Ideally should only show this R8-specific message when it is clear that R8 was
* used (e.g. when `c.getDeclaredConstructors().length == 0`), but on Android where this
* issue with R8 occurs most, R8 seems to keep some constructors for some reason while
* still making the class abstract
*/
return "Abstract classes can't be instantiated! Adjust the R8 configuration or register"
+ " an InstanceCreator or a TypeAdapter for this type. Class name: "
+ c.getName()
+ "\nSee "
+ TroubleshootingGuide.createUrl("r8-abstract-class");
}
return null;
}
public ObjectConstructor get(TypeToken typeToken) {
Type type = typeToken.getType();
Class rawType = typeToken.getRawType();
// first try an instance creator
@SuppressWarnings("unchecked") // types must agree
InstanceCreator typeCreator = (InstanceCreator) instanceCreators.get(type);
if (typeCreator != null) {
return () -> typeCreator.createInstance(type);
}
// Next try raw type match for instance creators
@SuppressWarnings("unchecked") // types must agree
InstanceCreator rawTypeCreator = (InstanceCreator) instanceCreators.get(rawType);
if (rawTypeCreator != null) {
return () -> rawTypeCreator.createInstance(type);
}
// First consider special constructors before checking for no-args constructors
// below to avoid matching internal no-args constructors which might be added in
// future JDK versions
ObjectConstructor specialConstructor = newSpecialCollectionConstructor(type, rawType);
if (specialConstructor != null) {
return specialConstructor;
}
FilterResult filterResult =
ReflectionAccessFilterHelper.getFilterResult(reflectionFilters, rawType);
ObjectConstructor defaultConstructor = newDefaultConstructor(rawType, filterResult);
if (defaultConstructor != null) {
return defaultConstructor;
}
ObjectConstructor defaultImplementation = newDefaultImplementationConstructor(type, rawType);
if (defaultImplementation != null) {
return defaultImplementation;
}
// Check whether type is instantiable; otherwise ReflectionAccessFilter recommendation
// of adjusting filter suggested below is irrelevant since it would not solve the problem
String exceptionMessage = checkInstantiable(rawType);
if (exceptionMessage != null) {
return () -> {
throw new JsonIOException(exceptionMessage);
};
}
// Consider usage of Unsafe as reflection, so don't use if BLOCK_ALL
// Additionally, since it is not calling any constructor at all, don't use if BLOCK_INACCESSIBLE
if (filterResult == FilterResult.ALLOW) {
// finally try unsafe
return newUnsafeAllocator(rawType);
} else {
String message =
"Unable to create instance of "
+ rawType
+ "; ReflectionAccessFilter does not permit using reflection or Unsafe. Register an"
+ " InstanceCreator or a TypeAdapter for this type or adjust the access filter to"
+ " allow using reflection.";
return () -> {
throw new JsonIOException(message);
};
}
}
/**
* Creates constructors for special JDK collection types which do not have a public no-args
* constructor.
*/
private static ObjectConstructor newSpecialCollectionConstructor(
Type type, Class rawType) {
if (EnumSet.class.isAssignableFrom(rawType)) {
return () -> {
if (type instanceof ParameterizedType) {
Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
if (elementType instanceof Class) {
@SuppressWarnings({"unchecked", "rawtypes"})
T set = (T) EnumSet.noneOf((Class) elementType);
return set;
} else {
throw new JsonIOException("Invalid EnumSet type: " + type.toString());
}
} else {
throw new JsonIOException("Invalid EnumSet type: " + type.toString());
}
};
}
// Only support creation of EnumMap, but not of custom subtypes; for them type parameters
// and constructor parameter might have completely different meaning
else if (rawType == EnumMap.class) {
return () -> {
if (type instanceof ParameterizedType) {
Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
if (elementType instanceof Class) {
@SuppressWarnings({"unchecked", "rawtypes"})
T map = (T) new EnumMap((Class) elementType);
return map;
} else {
throw new JsonIOException("Invalid EnumMap type: " + type.toString());
}
} else {
throw new JsonIOException("Invalid EnumMap type: " + type.toString());
}
};
}
return null;
}
private static ObjectConstructor newDefaultConstructor(
Class rawType, FilterResult filterResult) {
// Cannot invoke constructor of abstract class
if (Modifier.isAbstract(rawType.getModifiers())) {
return null;
}
Constructor constructor;
try {
constructor = rawType.getDeclaredConstructor();
} catch (NoSuchMethodException e) {
return null;
}
boolean canAccess =
filterResult == FilterResult.ALLOW
|| (ReflectionAccessFilterHelper.canAccess(constructor, null)
// Be a bit more lenient here for BLOCK_ALL; if constructor is accessible and public
// then allow calling it
&& (filterResult != FilterResult.BLOCK_ALL
|| Modifier.isPublic(constructor.getModifiers())));
if (!canAccess) {
String message =
"Unable to invoke no-args constructor of "
+ rawType
+ ";"
+ " constructor is not accessible and ReflectionAccessFilter does not permit making"
+ " it accessible. Register an InstanceCreator or a TypeAdapter for this type, change"
+ " the visibility of the constructor or adjust the access filter.";
return () -> {
throw new JsonIOException(message);
};
}
// Only try to make accessible if allowed; in all other cases checks above should
// have verified that constructor is accessible
if (filterResult == FilterResult.ALLOW) {
String exceptionMessage = ReflectionHelper.tryMakeAccessible(constructor);
if (exceptionMessage != null) {
/*
* Create ObjectConstructor which throws exception.
* This keeps backward compatibility (compared to returning `null` which
* would then choose another way of creating object).
* And it supports types which are only serialized but not deserialized
* (compared to directly throwing exception here), e.g. when runtime type
* of object is inaccessible, but compile-time type is accessible.
*/
return () -> {
// New exception is created every time to avoid keeping reference
// to exception with potentially long stack trace, causing a
// memory leak
throw new JsonIOException(exceptionMessage);
};
}
}
return () -> {
try {
@SuppressWarnings("unchecked") // T is the same raw type as is requested
T newInstance = (T) constructor.newInstance();
return newInstance;
}
// Note: InstantiationException should be impossible because check at start of method made
// sure that class is not abstract
catch (InstantiationException e) {
throw new RuntimeException(
"Failed to invoke constructor '"
+ ReflectionHelper.constructorToString(constructor)
+ "' with no args",
e);
} catch (InvocationTargetException e) {
// TODO: don't wrap if cause is unchecked?
// TODO: JsonParseException ?
throw new RuntimeException(
"Failed to invoke constructor '"
+ ReflectionHelper.constructorToString(constructor)
+ "' with no args",
e.getCause());
} catch (IllegalAccessException e) {
throw ReflectionHelper.createExceptionForUnexpectedIllegalAccess(e);
}
};
}
/** Constructors for common interface types like Map and List and their subtypes. */
@SuppressWarnings("unchecked") // use runtime checks to guarantee that 'T' is what it is
private static ObjectConstructor newDefaultImplementationConstructor(
Type type, Class rawType) {
/*
* IMPORTANT: Must only create instances for classes with public no-args constructor.
* For classes with special constructors / factory methods (e.g. EnumSet)
* `newSpecialCollectionConstructor` defined above must be used, to avoid no-args
* constructor check (which is called before this method) detecting internal no-args
* constructors which might be added in a future JDK version
*/
if (Collection.class.isAssignableFrom(rawType)) {
if (SortedSet.class.isAssignableFrom(rawType)) {
return () -> (T) new TreeSet<>();
} else if (Set.class.isAssignableFrom(rawType)) {
return () -> (T) new LinkedHashSet<>();
} else if (Queue.class.isAssignableFrom(rawType)) {
return () -> (T) new ArrayDeque<>();
} else {
return () -> (T) new ArrayList<>();
}
}
if (Map.class.isAssignableFrom(rawType)) {
if (ConcurrentNavigableMap.class.isAssignableFrom(rawType)) {
return () -> (T) new ConcurrentSkipListMap<>();
} else if (ConcurrentMap.class.isAssignableFrom(rawType)) {
return () -> (T) new ConcurrentHashMap<>();
} else if (SortedMap.class.isAssignableFrom(rawType)) {
return () -> (T) new TreeMap<>();
} else if (type instanceof ParameterizedType
&& !String.class.isAssignableFrom(
TypeToken.get(((ParameterizedType) type).getActualTypeArguments()[0]).getRawType())) {
return () -> (T) new LinkedHashMap<>();
} else {
return () -> (T) new LinkedTreeMap<>();
}
}
return null;
}
private ObjectConstructor newUnsafeAllocator(Class rawType) {
if (useJdkUnsafe) {
return () -> {
try {
@SuppressWarnings("unchecked")
T newInstance = (T) UnsafeAllocator.INSTANCE.newInstance(rawType);
return newInstance;
} catch (Exception e) {
throw new RuntimeException(
("Unable to create instance of "
+ rawType
+ ". Registering an InstanceCreator or a TypeAdapter for this type, or adding a"
+ " no-args constructor may fix this problem."),
e);
}
};
} else {
String exceptionMessage =
"Unable to create instance of "
+ rawType
+ "; usage of JDK Unsafe is disabled. Registering an InstanceCreator or a TypeAdapter"
+ " for this type, adding a no-args constructor, or enabling usage of JDK Unsafe may"
+ " fix this problem.";
// Check if R8 removed all constructors
if (rawType.getDeclaredConstructors().length == 0) {
// R8 with Unsafe disabled might not be common enough to warrant a separate Troubleshooting
// Guide entry
exceptionMessage +=
" Or adjust your R8 configuration to keep the no-args constructor of the class.";
}
// Separate effectively final variable to allow usage in the lambda below
String exceptionMessageF = exceptionMessage;
return () -> {
throw new JsonIOException(exceptionMessageF);
};
}
}
@Override
public String toString() {
return instanceCreators.toString();
}
}
© 2015 - 2025 Weber Informatics LLC | Privacy Policy